The present invention relates to potassium titanate which is used as an additive, etc., for plastics, friction materials, coating materials, lubricants, heat-resistant materials, heat-insulating materials, papers, etc., and particularly, to potassium titanate fine particles attaching importance to the configurational characteristics relative to a hygienic aspect.
Potassium titanate has essentially a fibrous form having a length of from several Am to several tens xcexcm, a diameter of 1 xcexcm or shorter, and a specific surface area of less than 20 m2/g, usually from about 5 to 10 m2/g, and by utilizing the fibrous form, potassium titanate has been practically used mainly as a reinforcement in the fields of plastics, coating material, frictional materials, etc., and has come into wide use at present. However, the fibrous powder of potassium titanate has the properties that the powder is bulky, the fluidity is inferior, and is hard to handle. Furthermore, the fibrous powder is liable to generate dusts, which cause a problem in working environment.
The carcinogenicity of asbestos has become a problem and there is a viewpoint that the cause thereof relates to the fibrous form. With regard to not only asbestos but also fiber materials, according to the Stanton""s hypothesis, it is said that fibers having a diameter of 0.25 xcexcm or shorter and a length of 8 xcexcm or longer have a high carcinogenicity. However, industrially useful fiber materials are utilized by establishing a standard in working environment. In ILO (International Labor Organization), fibers having a diameter of 3 xcexcm or shorter, a length of 5 xcexcm or longer, and the ratio of length to diameter of at least 3 are defined to be respirable fibers. Also, in AIA (Asbestos International Association) and DFG (Deutsche Forschungs Gemeinschaft), similar fibers are defined to be managed as fibrous dust.
The possibility that potassium titanate fibers give influences on the health of the respiratory organs, etc. is not clear, but when potassium titanate is used for the cases not requiring a fibrous use, it is desired that respirable fibers which are considered to be dangerous fiber size are not used.
The present invention has been made from the viewpoint of the safety and provides potassium titanate fine particles excellent in the configuration characteristics without having the form and the size of respirable fibers.
The invention has been developed for attaining the above-described object and provides potassium titanate fine particles made of the particles of potassium titanate having a length of shorter than 5 xcexcm.
Also, it is preferred that in the potassium titanate fine particles of the invention, the fine particles of potassium titanate having the length of shorter than 5 xcexcm and the ratio of the length to the breadth is less than 3 are from 70% to 100% by particle number.
Because the fibers having a length size of at least 5 xcexcm are defined to be respirable fibers in the standard of ILO, etc., the length of the potassium titanate fine particles is limited to shorter than 5 xcexcm in this invention.